The Matoran were the first beings created by the Great Beings for the Matoran Universe. The first to be created served as prototypes for the others - the Av-Matoran. Because they were the first ones, they had abilities to channel their innate light powers and transform into Bohrok. Eventually, the other types of Matoran were created. The Matoran were brought into existence even before Mata Nui, and were helping in his construction, though they didn't know what exactly they were building. Some Matoran, that showed particular promise, were allowed to go to the Artakha refuge and work in the light. After the Universe was built and Mata Nui awakened, the Matoran spread across the universe. They made their homes in many different enviroments and had many different styles of living. Some Matoran came to rely completely on the technology and inventions for work and protection, others grew completely independent, with no help from Toa, Turaga,or other beings. The Matoran's purpose after the universe was built was to do their work, to keep the universe in balance. The known jobs that Matoran performed are listed below:

Matoran usually tended to live in groups by elements, and in areas with climates that best suited their preferences; for example, water-loving Ga-Matoran chose to live together near the seas of Ga-Wahi, while the heat-resistant Ta-Matoran chose to live together in fiery places like Ta-Wahi. In hostile places like Voya Nui, however, Matoran of different types often had to live in the same area, regardless of whether or not it suited their environmental preferences. Sometimes they also lived alongside other species, like on Stelt. In most cases, Matoran settlements were led by Turaga, but when no Turaga were around, the Matoran either chose an alternative (like the Matoran of Mahri Nui formed the Mahri Nui Council and the elected Leader of the Mahri Nui Council), or remained leaderless.

The Matoran usually served the Great Spirit Mata Nui and the Great Beings. The Turaga often told them the Legend of Mata Nui, how he was sent from "Paradise", to give the Matoran a purpose. The Matoran had a work-based culture and upheld many virtues, primarily Unity, Duty and Destiny.

The Matoran often engaged in sporting activities. For example, a major sport in Metru Nui before the Great Cataclysm was Akilini. When the Matoran of Metru Nui migrated to Mata Nui, they invented a new game, called Kolhii. While on Mata Nui, the Turaga organized a Kolhii Tournament between the six Koros on the island. Of course, these two games weren't the only games the Matoran knew.

The Matoran spoke the language created for them by the Great Beings. This language was actually spoken by the whole Matoran Universe. Le-Matoran of Metru Nui, however, have created a slang called chutespeak (or treespeak), which combined two words into one. Chutespeak has also spread to other Matoran.

Matoran were classified by whichever Element they were affiliated with. Each type had a job, based on their attributes, to help keep the universe in balance. Although several were identified, there are more in existence.

Ta-Matoran, the Matoran of Fire, had a resistance to heat and valued diligence and responsibility.Ta-Matoran had shades of red as the color of their armor, though they were orange, yellow, and black as well. They were always male.

Ga-Matoran, the Matoran of Water, had a greater lung capacity than other Matoran, and were more agile underwater than other types of Matoran. They were peaceful and friendly, and were always female. Their armor was always in shades of blue.

Le-Matoran, the Matoran of Air, had heightened agility and reflexes. Le-Matoran were daring and lighthearted, take risks and enjoy a joke. They were always male, and their colors were shades of green, with some having turquoise as a secondary color.

Po-Matoran, the Matoran of Stone, had great physical strength. They tended to be down-to-earth and practical, not putting much stock in what they couldn't see and touch. They were always male, and their colors were shades of brown, tan, dull orange, black, and sometimes golden yellow.

Onu-Matoran, the Matoran of Earth, had increased strength and night vision, but could be blinded by bright lights. They often had respect for the past. Their armor was black, with dark grey, purple, tan, and occasionally orange as secondary colors. They were always male, and always had green eyes.

Ko-Matoran, Matoran of Ice, had a resistance to cold. They tended to be quiet to the point of being antisocial, and spent a lot of time being pondering the future. All Ko-Matoran were white, with shades of grey and blue as secondary colors. Their eyes were also always blue, and they were always male.

Av-Matoran, the Matoran of Light, were the first type of Matoran to be created. They had the ability to change their armor color and could shoot light bolts from energy swords. They could be either male or female. Their natural color scheme was gold and white.

Shadow Matoran were Matoran of other types who had their light drained, either by a Shadow Leech or a KanohiAvsa. Shadow was not a Matoran element. They were always aligned with Makuta, and had the ability to launch shadow bolts. Their colors were black and a murky shade of their previous colors, and their eyes were always reddish. They could be male or female, since any Matoran could become a Shadow Matoran.

Matoran were bio-mechanical beings, and were comprised of both organic and metallic Protodermis. They are generally short in stature, with child-like proportions and often with large feet compared to their legs. However, most of the details of their anatomy remain unknown. What is known is that they have been said to have had a circulatory system, and that they needed to breathe air to survive, and thus had lungs. Based on these, it is probable that their brains were also at least partially organic, though they were created with some basic knowledge and skills pre-programmed into them.

Matoran could be created by Mata Nui or whoever was in control of the Matoran Universe. All Matoran relied on powerless Kanohi magnetically attached to their faces that kept them "functioning"; a Matoran who lost his or her mask would quickly go into a coma-like state until their mask was returned or replaced. They didn't have the strength to activate the powers that Great Kanohi and Noble Kanohi held, but could sense that power was present if they wore such masks.

Matoran had a little bit of power of an element; just enough to influence their physical abilities. Matoran also had to "recharge" their energy occasionally in one of two ways; they either went to a power station and recharged once a year, or they "ate" by taking in energy from objects like fruit, berries and fish. Gender differences existed between the Matoran, but were not biological. Matoran could not biologically reproduce, and lacked the biological instincts to do so. However, it was not unheard of for Matoran to form deep, emotional bonds with one another.

Certain destined Matoran had special power hidden within them and when it was unleashed, the Matoran transformed into a Toa, with increased physical strength, size, and an Elemental Power. This power could be triggered in different ways, for example giving the Matoran Toa Power, or the energy of the Red Star, but if they were not destined they could not become Toa.

The average lifespan of a Matoran is unknown; there have been Matoran, Turaga and Toa who have long since passed the 100,000 year mark, yet none have shown any signs of aging whatsoever; in fact, of all the deaths that have occurred among the Matoran species, none were caused by old age. Theoretically, given the capacity for organic regeneration displayed by Toa, as well as the existence of the Red Star, the Matoran lifespan could be much greater than 100,000 years. However, it was possible for Matoran to age; this was confirmed by Mutran stating that, after transforming into pure energy, Makuta were no longer susceptible to aging and Helryx, the first and therefore oldest Toa, being described as being frail-looking for a Toa.

The Matoran were originally called "Tohunga". They were called Tohunga throughout the Mata Nui Online Game and the GameBoy Advance game, Bionicle: Tales of the Tohunga. Following the Maori lawsuit on LEGO in 2001, this had to be changed. In the re-release of Mata Nui Online Game, the name was changed to Matoran, and the GameBoy Advance game's title was changed to Bionicle: Quest for the Toa.

In Comic 1: Coming of the Toa, when Matoro meets Kopaka for the first time, he informs the Toa that he is a 'Tohunga'. This is non-canonical, however, and a mistake on the part of the comic's writers.